Is there any cheap parking for occasional parking on the weekends and weeknights? $7 is the going rate at Myer Centre, Wilson Parking and Wintergarden (after racq codes)? I know about $5 parking at King George Square but that's not prebooked so there's a chance you might not have a park once you get there.
Is there any prepay credit you can get cheaper from Cudo or GroupOn?
You can park on the street for free. Otherwise King George square has plenty of room unless there is a major event (NYE, Riverfire, etc.) going on.